The present invention relates to plumbing fixtures, and in particular to toilets provided with improved trapways.
Conventional toilets have a bowl and a flush tank cast in one or two pieces. A serpentine passage is formed in the toilet (or the bowl component of a two-piece toilet) to transport the contents of the bowl to an outlet opening that is usually at the bottom of the bowl. That opening is coupled to the waste plumbing lines of the building.
This passage is generally referred to as the bowl “siphon” or “trapway”. An upstream portion of this passage is normally filled with water, before and after a flush cycle, to “trap” sewer gases downstream thereof so as to prevent them entering the building interior. Water is maintained in the bowl and the upstream part of the trapway by forming an arched section that extends above the height of the bowl opening. The trapway (sometimes in conjunction with a jet passageway) generate a siphon to evacuate the bowl contents when the normally air/vapor-filled downstream portion of the trapway is rapidly filled with water during the flush cycle.
The trapway thus retains water in the bowl prior to flushing, and then assists in the formation of a siphon helpful in removing waste during the flush cycle. One common problem is to try to achieve this in low volume toilets. In this regard, for environmental and water conservation reasons many jurisdictions now restrict the sales of toilets which use too much water per flush. Thus, the water in the flush cycle must be used extremely efficiently.
To achieve a powerful flush, trapways are sometimes designed to maximize the flow rate and available volume of the trapway that can occupied during flushing. Various ways to accomplish this include specially shaping the flow path, controlling the state of flow (turbulent or laminar), and/or reducing or eliminating the occurrence of air pockets particular locations in the trapway. For example, U.S. Pat. No. 5,918,325 discloses a trapway modified in various ways to attempt to render flushing more optimal.
See also U.S. Pat. Nos. 3,484,873, 5,706,529 and 6,292,956. The disclosures of these patents, and of all other patents and publications referred to herein are incorporated by reference as if fully set forth herein.
However, prior art designs often did not adequately reduce or eliminate “blow back”, which is a reverse flow of air from the plumbing lines into a low pressure region of the trapway. To some extent, this obstructed flow through the trapway and caused a slower flush.
Accordingly, improved trapway designs were still needed, particularly in connection with low volume flush toilets.